The role of biopsy core number in selecting prostate cancer patients for active surveillance.

BACKGROUND

Studies offer wide variations in inclusion criteria for active surveillance (AS) in prostate cancer (PCa), but the role of the biopsy core number has not been thoroughly assessed.

OBJECTIVE

To evaluate the impact of the biopsy core number on the risk of misclassification for AS eligibility.

DESIGN, SETTING, AND PARTICIPANTS: This prospective study included 411 men eligible for AS who fulfilled at least one of four of the criteria reported in the literature groupings among a screening cohort of 2917 patients.

INTERVENTION

All patients underwent a 21-core biopsy with cores mapped by location and acted as controls of themselves for the analysis of biopsy core number (6-, 12- and 21-core schemes). Radical prostatectomy (RP) was performed in 297 men (72%).

MEASUREMENTS

The number of included patients, PCa extent on biopsy, rate of unfavorable disease in RP specimens, and biochemical recurrence-free survival were compared as a function of (1) the different criteria groupings for AS and (2) the biopsy core number (6, 12, or 21).

RESULTS AND LIMITATIONS

Of the 1104 patients with PCa, the proportion eligible for AS ranged from 22.5% to 35.4% based on AS criteria. In men who fulfilled AS criteria only in a 12-core strategy, tumor length and percentage of cancer involvement on biopsy were significantly greater than in those who fulfilled AS criteria in a 21-core scheme. The rate of unfavorable disease on RP specimens was also higher in the former group, from 28.6% to 35.9% relative to AS criteria (p=0.014, 0.044, and 0.113 in groups 2, 3, and 4, respectively).

CONCLUSIONS

Men eligible for AS based on a 21-core strategy have cancers with a lower extent of disease on biopsies and a lower risk of unfavorable disease on RP specimens regardless of how AS criteria are defined, compared with men eligible in a 12-core scheme.